1. Technical Field
The invention relates to the field of imaging systems and more particularly to a method and system for fusing image data from multiple sources.
2. Background Art
Multiple sensor imaging systems generate an image of an object by fusing data that is collected using multiple sensors. Gathering image data using multiple sensors, however, has posed challenges. In some systems, the sensors detect light received from separate apertures. Data generated from light from separate apertures, however, describe different points of view of an object that need to be reconciled in order to fuse the data into a single image. Additionally, using separate apertures for different sensors may increase the bulk of an imaging system.
In other systems, light from an aperture is split into components before entering the sensors. Reflective and refractive elements are typically used to direct the light to different sensors. For example, the system described in U.S. Pat. No. 5,729,376 to Hall et al. includes multiple reflective and refractive elements such as a lens that reflects light towards one sensor and refracts light towards another sensor. Each individual sensor, however, detects only a component of light, for example, only specific wavelengths of light, and thus cannot generate image data from the full spectrum. Additionally, multiple reflective and refractive elements may add to the bulk and weight of an imaging system. Consequently, gathering image data from multiple sensors has posed challenges for the design of imaging systems.
Yet other systems electronically combine the images generated from separate sensors. Image fusion involves combining two or more images produced by two or more image sensors into one single image. Producing one image that mitigates the weak aspects of the individual images while retaining the strong ones is a complicated task, often requiring a computer or processor with substantial computing power.
Generally, the prior attempts to fuse or combine images from a plurality of sensors into a single image generated a monochrome image where the only variable in the viewed combined image was a difference in light intensity or the intensity of a single color. Such monochrome images result in the loss of information to the viewer that is otherwise obtainable from the individual sensor images.
Further, it is known that the human eye has three different types of color sensitive cones. The response of the eye is best described in terms of three “tristimulus values.” However, it has been found that any color can be expressed in terms of the two color coordinates x and y.
The colors which can be matched by combining a given set of three primary colors (such as the blue, green, and red of a color television screen) are represented on a chromaticity diagram by a triangle joining the coordinates for the three colors.
Also, a typical night vision system that uses only a single sensor such as an image intensifier tube is a direct view system that means the axis of the user's eye is in optical alignment with the primary viewing axis of the image intensifier tube while the user looks at a phosphorous screen. Alternative systems using liquid crystal displays (LCD) or other electronic displays for viewing an image from a sensor are not axially aligned with the sensor generating the electronic image. For example, U.S. Pat. No. 4,786,966, issued 22 Nov. 1988, to Charles M. Hanson et al. teaches a head mounted display using a camera or sensor that is remote from the display such that the electronic display for viewing the image from a sensor is not axially aligned with the sensor generating the electronic image and the user's optical axis.
Additionally, multiple sensor units with coaxially aligned sensors are known and taught in U.S. Pat. No. 6,593,561, issued 15 Jul. 2003, to Antonio V. Bacarella et al., as an example. However, the alignment of the display and at least one of the sensors along a single optical axis is not disclosed.
U.S. Pat. No. 6,560,029, issued 5 May 2003, to Blair R. Dobbie et al., teaches a side mounted, man portable night vision goggle with an image from a thermal camera electronically fused with the images from a video camera on a display.
While the above cited references introduce and disclose a number of noteworthy advances and technological improvements within the art, none completely fulfills the specific objectives achieved by this invention.